Field of the Invention
The present invention relates to a substrate processing apparatus and a substrate processing method to perform certain process on a precision electronic substrate in the form of a semiconductor wafer or a thin plate such as a glass substrate for a liquid crystal display (hereinafter simply called a “substrate”) by discharging a processing liquid from a nozzle.
Description of the Background Art
In a conventional step of manufacturing a semiconductor device and the like, various processing liquids including deionized water, a photoresist liquid, and an etching liquid are supplied to a substrate to process the substrate by cleaning or applying a resist. A substrate processing apparatus that discharges a processing liquid to a surface of a substrate while rotating the substrate in a horizontal posture has widely been used as a processing apparatus that uses such processing liquids for processing.
In such a substrate processing apparatus, whether a processing liquid is discharged from a nozzle is determined by checking the output of a flowmeter or behavior of a pump. To determine the presence or absence of the discharge more reliably, Japanese Patent Application Laid-Open No. 11-329936 (1999) suggests a technique of directly monitoring discharge of a processing liquid from a nozzle by preparing imaging means such as a CCD camera, for example.
Where discharge of a processing liquid from a nozzle is to be directly monitored by imaging means, the background of an image being taken differs depending on the type of a target substrate. Specifically, various films including a resist film and an insulating film are generally formed on a surface of a substrate to form a pattern. The reflectance of the substrate surface differs largely depending on the respective types of these films or the resultant pattern. As a result, the background of an image being taken differs depending on the type of a target substrate. Even if films of the same type are formed, etching process for example with hydrofluoric acid corrodes the films further with elapse of processing time. This may change the reflectance of the substrate surface. Thus, noise in an image taken by the imaging means may be increased for various factors including the type of a film deposited on the surface, a resultant pattern, and the substance of processing. This makes it impossible to detect discharge of a processing liquid from a nozzle correctly.
According to the technique disclosed in Japanese Patent Application Laid-Open No. 11-329936 (1999), discharge of a processing liquid from the nozzle is monitored by the imaging means. This can for example detect dripping from a nozzle while failing to detect displacement of the nozzle itself. In a substrate processing apparatus, the nozzle from which a processing liquid is discharged can generally be moved between a standby position and a processing position for example by a rotary arm. The nozzle moves to the processing position predetermined by teaching according to given timing to discharge a processing liquid from the nozzle.
Meanwhile, due to an adjustment error caused during maintenance or temporal change, a processing liquid may be discharged from the nozzle having moved to a position displaced from the processing position determined by teaching. Such displacement of the nozzle makes it impossible to achieve an originally expected processing result.